Brown University researchers have developed a fully implantable and rechargeable wireless brain sensor capable of transmitting neural data to an external receiver. The system, which has performed remarkably well in monkeys and pigs for over a year, could eventually allow humans to control external devices with their thoughts.

The purpose of the project was to develop a neural interface device that could eventually help amputees, spinal cord injury victims, and those living with severe neuromotor disease (like Parkinson's) overcome their physical limitations. The challenge, however, was in developing a system that's safe, effective — and durable. Brain implants are not the kind of thing physicians want to be implanting and extracting on a regular basis. Ideally, the researchers wanted to create something that was small, low-power, leak-proof, and could last for decades.

Li-ion Batteries

To that end, David Borton and his colleagues developed a hermetically sealed implantable interface device that can be recharged by an external source.

They achieved this by using an embedded medical grade rechargeable Li-ion battery that can last for seven hours of continuous operation between recharges. It takes about two hours to refuel, with the incoming energy arriving from an inductive transcutaneous wireless power link at 2 MHz. Amazingly, the entire thing only requires 100 milliwatts of power to function.

During the early developmental stages, the researchers noticed that the recharging process caused it to heat up, which is obviously not good when you're talking about something that's connected to the brain. So, to resolve this problem, the researchers developed a liquid cooling system that uses chilled water.

A "Brain Radio"

The interface device is basically a "brain radio"; it transmits 24 Mbps via 3.2 and 3.8 Ghz microwave frequencies to an external receiver (which is about one meter away). The signals are transmitted in real-time by subjects who can move freely, and the data stream can relay information extracted from up to 100 neurons.

To make it work, a pill-sized chip of electrodes were implanted on a brain's motor cortex, which in turn relayed signals into the device's laser-welded, hermetically sealed titanium "can." It measures 2.2 inches (56 mm) long, 1.65 inches (42 mm) wide, and 0.35 inches (9 mm) thick. The entire signal processing system is contained within that tiny space, including the lithium ion battery, ultralow-power integrated circuits for signal processing and conversion, wireless radio and infrared transmitters, and a copper coil for recharging.

The researchers essentially established a point-to-point communication link for human clinical use. They can now use the system to observe, record, and analyze the signals emitted by scores of neurons in particular parts of the brain.

Capturing and Decoding Motor Activity

The brain-interface device was shown to work in six different animals, namely three pigs and three rhesus monkeys. "[The] wireless implant was electrically stable, effective in capturing and delivering broadband neural data, and safe for over one year of testing," noted the researchers in their study. "In addition, we have used the multichannel data from these mobile animal models to demonstrate the ability to decode neural population dynamics associated with motor activity."

No doubt, this is the very heart of the experiment. This information, once mapped, can be used for a variety of applications.

In particular, this implantable neural interface technology will greatly assist in the development of advanced neuroprostheses. Once refined and proven safe for humans, it could allow disabled people to move objects remotely with their thoughts. It would be a kind of technologically-enabled telekinesis. Indeed, the project is very closely linked to the BrainGate initiative — another Brown University project that's working to develop brain interface technologies for the disabled.

And of course, this technology will very likely trickle over to non-medical applications, allowing even able-bodied people to move objects with their minds.

In terms of next steps, Borton's team will be using a version of the device to study the role of the motor cortex in an animal model of Parkinson's disease. They will also work to reduce the size and cost of the device.